How the Tribune examined Chicago's speed camera program

Erin Hooley / Chicago Tribune

A speed camera tracks vehicles on 127th Street near the Major Taylor Bike Trail on Sept. 9, 2015, in Chicago’s West Pullman neighborhood. It has raised nearly $4 million in fines since the enforcement program’s inception, making it the city's top ticketing camera.

A speed camera tracks vehicles on 127th Street near the Major Taylor Bike Trail on Sept. 9, 2015, in Chicago’s West Pullman neighborhood. It has raised nearly $4 million in fines since the enforcement program’s inception, making it the city's top ticketing camera.

To examine Chicago's speed camera program, the Chicago Tribune used the state Freedom of Information Act to obtain numerous records, including data from every violation recorded since the first camera began generating tickets in October 2013 and continuing through Sept. 1.

The Tribune also obtained records documenting all 33,474 ticket appeals through Sept. 1, Chicago crash data dating back to 2004 and Chicago Park District construction schedules since the inception of the camera program.

Those records provided details of more than 2.1 million citations, including warning notices and fines for either $35 or $100. The ticket records include a unique violation number; the issuing camera by address, school or park zone the camera is attached to; date and time; type of vehicle; license plate; vehicle speed; speed limit; and the fine amount or whether it was a warning. The records did not include personally identifying information.

The appeals records contain largely the same information plus the name of the presiding hearing officer, the outcome of the appeal, the reason for the outcome and any additional notes the hearing officer chose to make in the record at the time of the appeal.

By checking the dates of speed camera citations against the construction schedule of parks, the Tribune was able to pinpoint when the cameras were improperly issuing tickets near closed parks.

By checking when the city's hearing officers overturned tickets on grounds that the required signs were legally insufficient, the Tribune was able to identify specific cameras with that problem. The Tribune defined an ongoing problem with inadequate signs when at least two hearing officers overturned tickets from a camera at least five times within 12 months for reasons involving inadequate signage.

State law requires the presence of a schoolchild for the city to issue reduced-speed citations in school zones. That means a schoolchild must be in the images posted online for review by the ticket holders. In more than 1,200 cases, city hearing officers overturned appealed tickets on grounds that evidence of a child was insufficient.

To understand how pervasive the problem might be, the Tribune reviewed the evidence in a computer-generated random sample of 1,500 tickets in which the city enforced a reduced speed limit in a school zone. The Tribune did not consider speeding tickets issued to vehicles exceeding 41 mph, because those drivers would face the maximum penalty regardless of whether a child was in the photo.

It also obtained the list of guidelines that ticket processors working for the city and its contractors are supposed to use when determining whether a pedestrian in the image is a child.

Applying those guidelines, the Tribune found a child to be present in 699 of the 1,500 cases, or 46.6 percent, with no visible evidence of a child in 799 cases, or 53.3 percent of the tickets. There were no photos available online for two cases in the sample.

Applying that initial finding to the total of more than 352,000 tickets issued in the reduced-speed zones suggests that more than 188,000 tickets were issued without the sufficient evidence.

Because the photographic evidence available to the city's ticket processors allows them to zoom in and enhance images in ways the public cannot, the Tribune obtained the raw, high-quality images in 50 cases of the sample. Those cases were neither sorted nor randomly generated but rather taken from the list of 800 tickets in which the Tribune found a problem.

The city doled out $100 tickets because it said there was a child in each of these 11 photos, but a Tribune review found that evidence lacking.

(City of Chicago speed cameras)

In a review that included representatives of the city's speed camera vendor, American Traffic Solutions, the Tribune found evidence of a child in 21 of the 50 cases in the second sample, or 42 percent. The second review found no evidence of a child in 29 cases, or 58 percent, of the second sample.

By multiplying the percentages in both samples, the analysis concluded that 31.5 percent of the random sample tickets were issued without adequate evidence of a child, suggesting that more than 110,000 tickets were likely issued in error over the life of the 2-year-old program.

The Tribune's methodology and findings were reviewed by Bruce Spencer, a Northwestern University statistics professor, and undergraduate student Claire Langlotz. They determined that the methodology of the "two-phase sampling" was sound and calculated that because of the small size of the second sample, it had a margin of error of 7.8 percent.

The best estimate of the problem is 110,000, but the number could be as low as 83,000 or as high as 137,000, given the margin of error, Spencer said.

To express the potential value of those tickets in fines, the Tribune multiplied the total value of the 352,000 reduced-speed tickets, which is more than $13 million, by the sample finding of 31.5 percent.

A version of this article appeared in print on November 18, 2015, in the News section of the Chicago Tribune with the headline "How the Tribune examined the speed camera program" —
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